The overall goal of this project is the development of an interactive, image-guided system for accurately placing ablation lesions in the left atrium for the treatment of arrythmias. Atrial fibrillation (AF) affects 10% of the population over age 70 and causes about 1/3 of strokes. Only 2/3 of percutaneous procedures for AF succeed even in carefully selected patients due to technical limitations in both visualizing tissue/device interaction and controlling catheter position. We believe that the combination in a single procedure of real-time visualization and guidance, interactive device control, and immediate lesion assessment will be critical in providing reliable, robust atrial ablation and will increase effectiveness far beyond the sum of the individual parts. Guidance and visualization will be provided by MRI, which permits real-time anatomic visualization, allows active tracking of devices, and provides many techniques for ablation monitoring and control. Intuitive, accurate access to the entire left atrium will be accomplished via an interactive, feedback controlled catheter manipulation system integrated with a real-time 3D visualization environment for navigation and device placement. This system will incorporate a haptic interface for robotic control integrating MR visual feedback catheter force feedback. Finally, direct MR visualization of acute lesions will provide immediate verification of ablative success. Imaging the lesion development will be accomplished via delayed enhancement, T2 weighted imaging, and a new MR RF current mapping technique that can potentially highlight tissue conductivity changes in the myocardium post-ablation. Specifically, our aims are to: 1) Develop improved MRI methods and devices for real-time 3D guidance during cardiac ablations. 2) Develop a general purpose intracardiac catheter system integrating sensory inputs and motor controls to provide precise control of the interventional catheter. 3) Develop and test real-time methods to assess tissue viability and electrical conductivity that can accurately predict and visualize the ablation pattern. The combination of visualization, guidance, and verification will allow quick, reliable atrial ablations, dramatically improving patient outcomes. The overarching objective of this proposal is to develop an integrated set of technologies to enable the imaging, mechanical, and control systems needed to replicate the surgeon's visualization, dexterity, and tools for performing percutaneous intracardiac surgery. This project will utilize a multi-disciplinary team (engineers, imaging scientists, and cardiologists) to address all the technical challenges in translating this system to clinical practice. Our initial focus will be intracardiac ablation of atrial fibrillation, given its prevalence, substantial clinical impact, and current suboptimal percutaneous success. This research - developing a minimally invasive system for atrial fibrillation procedures - is important to public health because it may allow many open-heart surgery procedures to be performed instead using less invasive catheters. This research also initially targets atrial fibrillation as it is very common (1 in 4 Americans develop it in their lifetime), leads to 1/3 of strokes, and there is a need for a successful method to cure it less invasively.